1. Field of the Invention
The present invention relates generally to heat exchanger devices, and more particularly to a compact heat exchanger with corrugated polymeric tubing for use with high purity and/or corrosive fluids.
2. Description of the Background Art
Many industries require the use of heat exchangers to regulate the temperature of high purity and/or corrosive fluids. For example, microchip fabrication within the semiconductor industry requires heating and temperature regulation of the etching solutions used to etch silicon wafers and microcircuit lines. Because both the process temperatures and the heat capacities of the etching fluids are relatively high, a rather large amount of heat is required to raise and maintain the temperatures of the etchants.
Additionally, etching fluids must be free of foreign particles in order to avoid the contamination and destruction of microcircuits formed in the silicon wafers. Therefore, because etching chemicals, such as hydrofluoric acid, are harsh and corrosive, the etching fluid must not come in contact with any portion of the heat exchanger which could corrode and/or dissolve, thereby introducing contaminants into the etchant.
Attempts have been made to overcome these limitations. For example, thermally conductive oil or grease is often placed between the tube and heat exchanger. Additionally, coiled inserts are sometimes placed within the tube (see e.g., U.S. Pat. No. 5,899,077 to Wright, et al.). While the turbulence caused by the inserts facilitates increased thermal transfer between the heat exchanger and the fluid, the inserts also cause “dead zones” within the fluid flow, increasing the potential for particle build-up and contamination of the etching fluid.
In addition, it is also hard to form tight bends in known tubing materials. This creates several problems when designing and manufacturing heat exchangers, wherein tubing typically includes multiple bends. First, known inert tubing is easily kinked, and cannot therefore be bent into small diameter bends. Rather, such tubing requires a large bend radius, and is therefore often bent outside of the heat exchanger, thereby reducing the heating efficiency of the heat exchanger. Further, as the wall thickness of the tubing decreases, the required bend radius increases. Alternately, if the tubing is entirely retained within the heat exchanger, a complex curved channel with large bend radii must be machined into the heat exchanger plating. In either situation, because of the large bend radii of plastic tubing, less tubing can be used per unit surface area of the heat exchanger, thereby reducing the thermal efficiency of the heat exchanger.
What is needed, therefore, is a heat exchanger that utilizes tubing that can withstand high working temperatures without rupturing or becoming diffusive. What is also needed is a heat exchanger that improves thermal conductivity between the tube and the heat exchanger, while remaining compact, highly expandable, inexpensive to produce, and easy to maintain.